Arthroplasty systems and methods for optimally aligning and tensioning a knee prosthesis

ABSTRACT

A combination of a first assembly for guiding resection of a femur and tibia of a knee joint and a second assembly including femoral and tibial knee components. The combination of the first assembly and the second assembly provides optimal placement and positioning of the femoral and tibial knee components to achieve near-normal knee kinematics and tension. The preparation for and placement of the prosthetic knee components provides medial-pivoting kinematics mimicking that of the natural knee thereby promoting improved outcome for the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/351,135,filed Nov. 14, 2016, which is a continuation of U.S. patent applicationSer. No. 14/531,749, filed Nov. 3, 2014, and entitled ARTHROPLASTYSYSTEMS AND METHODS FOR OPTIMALLY ALIGNING AND TENSIONING A KNEEPROSTHESIS (now issued as U.S. Pat. No. 9,492,180), which is acontinuation of U.S. patent application Ser. No. 13/685,660, filed Nov.26, 2012 and entitled ARTHROPLASTY SYSTEMS AND METHODS FOR OPTIMALLYALIGNING AND TENSIONING A KNEE PROSTHESIS (now issued as U.S. Pat. No.8,876,831), which is a continuation of U.S. patent application Ser. No.12/191,262, filed Aug. 13, 2008 and entitled ARTHROPLASTY SYSTEMS ANDMETHODS FOR OPTIMALLY ALIGNING AND TENSIONING A KNEE PROSTHESIS (nowissued as U.S. Pat. No. 8,317,797), which is a continuation-in-part ofU.S. patent application Ser. No. 11/349,772, filed Feb. 8, 2006, andentitled GUIDE ASSEMBLY FOR GUIDING CUTS TO A FEMUR AND TIBIA DURING AKNEE ARTHROPLASTY (now issued as U.S. Pat. No. 7,927,336), which claimspriority to U.S. Provisional Patent Application Ser. No. 60/651,102,filed Feb. 8, 2005 and entitled GUIDE ASSEMBLY FOR GUIDING CUTS TO AFEMUR AND TIBIA DURING A KNEE ARTHROPLASTY, each of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is related to the use of instruments for guidingpreparation of a knee for installation of an implant during anarthroplasty, and in particular, to the use of ligaments around the kneeand other anatomical features to position the guide instruments andmaking reference cuts to the tibia and the femur.

Description of Related Art

During a knee arthroplasty, a surgeon typically must gain access to theknee joint in order to perform resections of existing bone and cartilageso as to shape the tibia and femur to fit mating surfaces of theimplant. Some arthroplasty procedures seek to minimize the invasivenessof the approach to the knee joint by minimizing the size of the incisionin the surrounding soft tissue structure of the knee and the patella.Preserving the soft tissue structure also preserves some of the supportprovided by these tissues. However, preserving the soft tissuessurrounding the knee can be difficult at times due to the need to firmlysupport the resection guides relative to the bone of the tibia and thefemur.

The manner in which the natural knee joint performs is largely affectedby the tension in the collateral ligaments of the knee, as well as bythe alignment of the articular surfaces of the knee joint relative tothe collateral ligaments. In the natural knee joint, the plane of thearticular surfaces of the femur and the tibia bisects the collateralligaments at an optimal, physiological position. This optimal,physiological position enables the knee joint to flex and extend in abalanced and properly aligned manner. Exemplary arthroplasty proceduresresection the femur and the tibia, yet preserve the optimal,physiological position of the knee joint when fitted with a prosthesis.

Preservation of the ligamentous and other soft tissue structures aroundthe knee can provide a reference point for accurately positioning thetibial and femoral components of the knee implant, in particular whensaid structure is in tensed or otherwise loaded condition. For example,ligament tensions can be used to guide placement of resection guides.Conversely, preservation of the soft tissue structures requiresbalancing of the forces exerted by the soft tissues to promote normalkinematics in the knee and normal patellar tracking. Therefore, ligamentforces can play a significant role in restoring normal function to aknee. Generally, therefore, reductions in the invasiveness of the kneearthroplasty procedure combined with improvements in the positioning andinstallation of knee components can result in a better overall surgicaloutcome for the patient.

It would therefore be advantageous to have instrumentation for guidingresection of the femur, tibia and other structures in the knee during aknee arthroplasty that works well with minimally invasive approaches tothe tibia and femur. It would be further advantageous if theinstrumentation assisted the balancing of forces between the kneeimplant components and the preserved ligamentous and soft tissuestructures for improved function of the knee implant. Also, it would beadvantageous to have instrumentation for guiding resection that uses theligamentous structure of the knee to guide placement of theinstrumentation and the resulting optimal alignment and physiologicalpositioning of the knee prosthesis.

BRIEF SUMMARY OF THE INVENTION

The present invention meets the above needs, and achieves otheradvantages, by providing an assembly for guiding resection of a femurand tibia of a knee joint in preparation for installing femoral andtibial knee components. The components of the present invention may beconfigured for use in both total knee replacement and unicompartmental,or partial knee arthroplasty. Embodiments of the present assembly caninclude tibial and femoral IM rods which are connected through a torquebolt that allows controlled adjustment of the distraction of the tibiaand femur during cut positioning in a range of flexion angles. Also, theassembly is usable with relatively small, noninvasive approaches to theknee joint by way of relatively narrow, low profile components thatattach to tibial and femoral IM rods. Further, the assembly includesseveral quick-release components to allow fast assembly and disassemblyin a surgical setting. Each of these aspects, along with the ability ofthe assembly to accurately guide initial reference cuts to the tibia andfemur, promotes an improved outcome for the patient.

An assembly of one embodiment of the present invention includes femoraland tibial IM rods, a flexion cutting guide, an extension cutting guideand a selection of selectively lockable components. Each of the IM rodsincludes a shaft portion that is configured to extend within the IMcanal of the femur or tibia. The femoral IM rod also includes a femoralmount on an end of the shaft that is configured to extend away from thefemur when the shaft is in the femoral IM canal. Similarly, the tibialIM rod includes a tibial mount on an end of the shaft that is configuredto extend away from the tibia when the shaft is in the tibial IM canal.Each of the mounts is configured to attach to one or more of theselectively lockable components. The flexion and extension cuttingguides define one or more slots wherein the slots are configured toguide the use of cutting and other instruments to make preparatory cutsto the femur and/or the tibia with the knee in flexion and extension.Each of the cutting guides is configured to attach to one or more of theselectively lockable components so as to be supported by the femoral andtibial IM rods. The selectively lockable components are configured toattach to the femoral and tibial IM rods, to have at least one portionwith a relatively small cross section extending anteriorly oranterior-medial out of the knee joint compartment and to attach to theflexion and extension cutting guides and support and limit the motionthereof.

In one aspect, the femoral mount has a cylindrical shape that extends inan anterior-posterior direction between the femoral condyles andincludes a central opening and a plurality of gauge marks extendingalong its outside surface. The central opening may also include ananterior anti-rotation portion (e.g., a hexagonal shaped portion) and alarger diameter cylindrical portion. The tibial mount can include orsupport a flexion bolt with a threaded shaft at one end configured toextend into an opening in the tibial IM shaft, a bushing at the otherend and an exterior hexagonal flange in between the ends. The bushing isconfigured to extend into the cylindrical portion and also contains aninterior hexagonal bore. The hexagonal flange is configured to allowgripping by an external torque wrench or internal torque driver to urgethe femoral mount away from the tibial mount (by turning of the threadedshaft) and distract the tibia and femur to a desired torque reading.This allows the surgeon to apply the appropriate amount of tension tothe ligamentous structure as defined by said surgeon and recorded forcomparison later in the technique.

Included in an exemplary embodiment of the selectively lockablecomponents is a first locking mechanism that has an arm, a plungerassembly and an anti-rotation extension, defined in this instance as ahex. The arm has an elongate portion extending away from a head portion.Also extending from the head portion is the hex-shaped anti-rotationextension. Defined through the head portion and hex extension is anopening that is configured to receive a shaft of the plunger assembly.The plunger assembly includes a thumb press at one end of the shaft andan anti-rotation feature similar to anti-rotation extension, defined inthis instance as a hexagonal tip at the other end of the shaft thatextends out of the hex extension. Also, the shaft includes a peg thatextends into a helically shaped slot defined in the head portion. Aspring extends between the head portion and the thumb press. Depressionof the thumb press advances the shaft, while the peg and helical slotcause the shaft to rotate, and the flats of the hexagonal tip to alignwith the hex extension. This allows the hexagonal tip and hex extensionto become concentric and to be inserted into the anterior hex portion ofthe central opening of the femoral mount. In addition, the hexagonal tipis configured to extend out of the hex portion of the opening and intothe cylindrical portion, and to rotate (due to the helical slot and peg)into an eccentric position upon release of the thumb press, therebylocking the locking mechanism into the femoral mount. When attached, thehead portion of the arm extends proximally out of the knee jointcompartment and the elongate portion extends anteriorly (with respect tothe tibia) through the surgical incision.

A flexion guide support member of the assembly of the present inventionincludes a slider member and a ratchet bar. The slider member isconfigured to attach to, and slide along, the elongate portion of thearm of the first locking mechanism, such as by having an opening definedtherein matching the cross-section of the elongate portion. The ratchetbar is configured to extend toward a plane defined by the tibialplateau. Preferably, when assembled, the femoral mount, first lockingmechanism and flexion guide support member roughly form a U-shape thatis relatively narrow in the medial-lateral direction to allow its usewith narrow incisions.

Also included in the selectively lockable components is a quick releasemechanism that is configured to slide along and lock to the ratchet barof the flexion guide support member. For example, the quick releasemechanism may define an opening configured to extend and slide along theratchet bar, and a locking pin that is spring loaded to extend into aportion of the ratchet to stop the sliding motion. The locking pin isspring biased, but can be overcome with a manual draw pull (for example)to allow further sliding or repositioning of the quick releasemechanism. The quick release mechanism may also include a spring-biasedlocking lever that, along with an engagement member of the quick releasemechanism, can extend into an opening and lock to the flexion cuttingguide. Depressing the locking lever again easily releases the flexioncutting guide after k-wire or other fasteners have been used to securethe flexion cutting guide in place to the tibia or femur. This allowsthe resection guide to translate toward the proximal tibia and away fromthe tensioning assembly with the knee in flexion.

Once the flexion resection guide is fixed to the proximal tibia, theresection guide has a plurality of slots for which to resect multiplecomponents of the femur and tibia, most notably a measured proximaltibial resection and a posterior condylar resection. Making theseresections with the knee in tension at 90 degrees will allow the user totheoretically make a tensed flexion gap resection.

The selectively lockable components may also include componentsconfigured to attach to the femoral and tibial IM rods when the knee isin extension. For example, the components may include a cannulatedextension bolt, a tibial angulation guide, an extension guide supportmember and a second locking mechanism. The tibial angulation guide isconfigured to attach to the tibial IM rod through the cannulatedextension bolt which is, in turn, coupled to the tibial IM rod andextend around the femoral mount, such as by having a block defining anarc-shaped channel that is configured to receive the cylindrical outersurface of the femoral mount. Included on the tibial angulation guideare a plurality of gauge marks that, when correlated to gauge marks onthe outer surface of the femoral mount, register an amount of valgusangulation of the tibia with respect to the femur. The tibial angulationguide may be configured to extend into the bushing of the bolt describedabove, or to have its own threaded shaft and hexagonal flange allowingit to be used to distract the tibia and femur in extension to a torquevalue corresponding to the torque value previously measured with theknee in flexion.

The extension guide support member is configured to have a relativelynarrow profile and extend anteriorly out of the joint compartmentthrough the incision providing access thereto. For example, theextension guide support member may include a mounting portion that iscylindrical and defines a cylindrical opening and a support arm that isconfigured to extend proximally from the mounting portion. The secondlocking mechanism is generally configured similar to the first, exceptit lacks the fixed elongate portion of the arm. Rather, it includes acylindrical head portion that is configured to extend through thecylindrical opening of the mounting portion of the extension guidesupport member so as to connect the extension guide support member tothe femoral mount while allowing said support member to rotate in adesired position independent of the previously selected valgus angle.

The extension guide support member also includes a support arm that isconfigured to extend proximally from the mounting portion when themounting portion is attached to the femoral mount using the secondlocking member. The extension cutting guide is configured to slidablyattach over the support arm, such as via a channel defined in its body.Also, the extension cutting guide preferably includes a swivel arm thatcan be swung into an abutting relationship with the tibial plateau andthe plateau flange of the tibial mount to provide an additionalreference point for making a femoral resection with the knee inextension. The extension cutting guide, similar to the flexion cuttingguide, may also define a plurality of fixation openings allowingfasteners to extend therethrough and attach the extension cutting guideto the tibia or femur. This allows removal of the selectively lockablecomponents to provide room for the cuts to the tibia and/or the femur.

The swivel arm, once referenced off the proximal tibial resection, willallow the extension cutting guide to make a pre-determined resection ofthe distal femur. Resecting with the knee tensed in the extendedposition will allow the user to make a balanced extension gap resectionwhen compared with the tensed resections made with the knee previouslypositioned in flexion.

The assembly of the present invention has many advantages. For example,it provides a relatively narrow and low profile collection of lockingcomponents that securely attach cutting guides to tibial and/or femoralIM rods. This provides a robust guide to reference cuts being made tothe tibia and the femur with an approach to the joint that minimizesinvasiveness. Further, many of the components, such as the first andsecond locking mechanisms and the quick release mechanism, facilitatequick assembly, easy adjustment and quick disassembly for improvedefficiency. Additionally, the use of the flexion bolt in flexion and theextension bolt in extension, combined with the other components of thetensioning assembly, allow the tibia and femur to be distracted under amatching amount of tension in flexion and extension to ensure a betterfit for the tibial and femoral knee replacement components throughout arange of flexion. Spacers, as well as limited radial movement of thetensioning assembly components further allow the knee to adjust toaccommodate the natural physiology of the patient's knee throughout thetensioning and resection processes. Thus, the described procedures andassemblies allow the surgeon to adjust the amount of valgus angulationof the tibia as desired to match the anatomy of the patient.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a plan view of a tibial intramedullary (IM) rod and femoral IMrod of an assembly of one embodiment of the present invention;

FIG. 2 is a perspective view of the femoral IM rod of FIG. 1 insertedinto a femur;

FIG. 3 is a cross-section of a femoral mount of the femoral IM rod shownin FIG. 2;

FIG. 4 is a perspective view of a femoral and tibial IM rods of FIG. 1inserted in the femur and tibia of a knee, respectively;

FIG. 5 is a perspective view of a bushing extending from an extensionbolt of the assembly of the present invention wherein the extension boltis coupled to the tibial IM rod of FIG. 1;

FIG. 6 is a plan view of the extension bolt of FIG. 5 and of a tibialangulation guide and flexed knee cutting guide of the assembly of thepresent invention;

FIG. 7 is a perspective view of the bushing and IM rods of FIG. 5,wherein the bushing of the extension bolt is advanced to connect the IMrods;

FIG. 8 is a side elevation view of a first locking mechanism of theassembly of the present invention;

FIG. 9 is a perspective view of the first locking mechanism beingconnected to the assembled IM rods and bolt of FIG. 7, torqued to adesired load;

FIG. 10 is another perspective view of the first locking mechanism inthe unlocked position, assembled IM rods and bolt of FIG. 9, torqued toa desired load;

FIG. 11 is yet another perspective view of the first locking mechanismassembled and locked to the IM rods and extension bolt of FIG. 9,torqued to a desired load;

FIG. 12 is a perspective view of a flexion guide support member of theassembly of the present invention connected to the first lockingmechanism of FIG. 11;

FIG. 13 is a perspective view of a flexed knee cutting guide assembly ofthe assembly of the present invention connected to the flexion guidesupport member of FIG. 12;

FIG. 14 is a side elevation view of the assembly of FIG. 13;

FIG. 15 is a rear elevation view of the assembly of FIG. 13;

FIG. 16 is a bottom elevation view of a quick release mechanism of theflexed knee cutting guide assembly of FIG. 13;

FIG. 17 is a perspective view of the quick release mechanism of FIG. 16and the flexion guide support member of FIG. 12;

FIG. 18 is a perspective view of a flexed knee cutting guide of theflexed knee cutting guide assembly of FIG. 13;

FIG. 19 is a front elevation view of a tibial angulation guide of theassembly of the present invention extending between the femoral andtibial IM rods of FIG. 1, coupled with an extension bolt;

FIG. 20 is an enlarged view of the IM rods and tibial angulation guideof FIG. 19;

FIG. 21 is another enlarged view of the IM rods and tibial angulationguide of FIG. 19;

FIG. 22 is a perspective view of a second locking mechanism andextension guide support member of the assembly of the present inventionbeing assembled to the femoral IM rod of FIG. 1;

FIG. 23 is an enlarged perspective view of the assembly of the extensionguide support member of the present invention to the second lockingmechanism of FIG. 22;

FIG. 24-26 are various a perspective views of an extended knee cuttingguide of the assembly of the present invention attached to the extensionguide support member and second locking mechanism of FIG. 22, and thefemoral IM rod of FIG. 1;

FIG. 27 is a perspective view illustrating disassembly of the secondlocking mechanism of FIG. 22, from the femoral IM rod of FIG. 1, oncethe extended knee cutting guide is fixed in position to the distalfemur;

FIG. 28 is a front elevation view of the extended knee cutting guide ofFIG. 24;

FIG. 29 is a side elevation view of the extended knee cutting guide ofFIG. 24;

FIG. 30 is a plan view of an L-shaped cutting block of the assembly thepresent invention;

FIG. 31 is a side elevation view of the L-shaped cutting block of FIG.30 being used to cut an anterior condyle of a femur;

FIGS. 32-40 show various modular options of the present invention thatpromote quick assembly and facilitate minimally invasive intra-operativeuse;

FIG. 41 shows a hinged retractor as used in one embodiment of thepresent invention;

FIG. 42 shows an embodiment of the present invention that implementsmini-trials;

FIG. 43 shows an exploded view of an embodiment of the present inventionfor resection in knee flexion;

FIG. 44 shows a perspective view of the assembled embodiment of FIG. 43;

FIG. 44A shows a perspective view of an implementation of the currentinvention having a ratcheting device in place of the flexion bolt;

FIG. 45 shows a perspective view of an embodiment of the presentinvention having the cutting block attached and secured;

FIG. 46 shows an exploded view of an embodiment of the present inventionfor resection in knee extension;

FIG. 47 shows a perspective side view of the assembled embodiment ofFIG. 46;

FIG. 48 shows a perspective view of an embodiment of the presentinvention having the cutting block attached and secured;

FIG. 49 shows a perspective front view of an embodiment of theresectioned knee having been fitted with a knee prosthesis;

FIG. 50 shows a perspective side view of the embodiment of FIG. 49; and

FIG. 51 shows a partially cross-sectioned view of an implementation ofthe knee prosthesis.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments of the invention are shown. Indeed, this invention may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

An assembly 10 of the present invention for facilitating preparation ofa knee joint, including guiding positioning of cuts to a femur 11 andtibia 12 of the knee joint, for later mating with femoral and tibialknee replacement components, is shown in the accompanying figures.Generally, the assembly 10 includes various components selected andarranged to attach to a reference point inside the knee jointcompartment (such as one or more intramedullary (IM) rods), extendthrough a relatively narrow, small or noninvasive approach defined inthe soft-tissues of the knee and attach outside the knee to a selectionof resection guides.

Anatomical directions as used herein are in reference to the knee duringthe preparatory surgery and correspond to the illustrated embodiment ofthe assembly 10. However, depending upon the handedness of the knee, orvariations in individual morphology and ligamentous structure, thesedirections could vary and should not typically be considered limiting.

The assembly 10 can be configured to be applied at different kneeflexion angles to facilitate positioning of the components throughoutthe range of flexion or extension. Illustrated herein are components ofthe assembly 10 for guiding cuts and preparation of the knee at twodifferent flexion angles, namely 90° and full extension. However, thecomponents can be adjusted or configured, or other components employedwithin the spirit and scope of the present invention, to extend throughrelatively non-invasive approaches to the knee joint at any range offlexion be it hyper-extension, 30°, 45°, 60°, etc., through tohyper-flexion.

In the illustrated embodiment, the assembly 10 includes two IM rods, afemoral IM rod 13 and a tibial IM rod 14 that provide a reference pointfor supporting the remainder of the assembly 10 with the knee inflexion, in this case 90° of flexion. The femoral IM rod 13 includes afemoral mount 15 and a main shaft 16, as shown in FIG. 1. The main shaft16 of the femoral IM rod 13 is preferably an elongate, relatively rigidshaft that, when installed, extends within the IM canal of the femur 11in a proximal-distal direction, as shown in FIG. 2. The main shaft 16can include structure that facilitates its insertion into the femur 11,such as a tapered end 17. Preferably, the main shaft 16 is constructedof a relatively rigid material, such as a hard plastic, stainless steel,titanium or other metal or material that is capable of insertion intobone without damage and of stably supporting the femoral mount 15.

Attached to the distal end of the main shaft 16, opposite the taperedend 17, is the femoral mount 15. Generally, the femoral mount has acylindrical shape with an axis extending perpendicular to a long axis ofthe main shaft 16. Defined along the axis of the femoral mount 15 is acentral opening 18, as shown by the cross-sectional view of the femoralmount in FIG. 3. The central opening includes two portions, ananti-rotation portion, in this instance a hex portion, 19 and acylindrical portion 20 which allow locking of other components of theassembly 10 to the femoral mount 15, as will be described in greaterdetail below. Regardless, once the femoral IM rod 13 is installed, thefemoral mount 15 and its central opening 18 preferably extend in ananterior-posterior direction along the femoral notch between the femoralcondyles. Defined on the outer cylindrical surface of the femoral mount15 is a plurality of longitudinally extending gauge marks 21 that aid inpositioning of the tibial and femoral components, as will be describedin more detail below.

As shown in FIGS. 1 and 4, the tibial IM rod 14 includes a main shaft 22supporting a tibial mount 23. Similar to the main shaft 16 of thefemoral IM rod 13, the main shaft 22 has an elongate structure with atapered distal end 24 to facilitate its insertion into the IM canal ofthe tibia. However, the main shaft 22 preferably includes one or moreflutes 25 extending along its length in order to further facilitateinsertion and to resist rotation within the IM canal of the tibia. Theseflutes may also, optionally, be included on the main shaft 16. Definedin the main shaft 22 at its proximal end is an opening 27 that extendsinto the flutes 25. These openings further facilitate insertion into theIM canal of the tibia. As with the main shaft 16 of the femoral IM rod13, the main shaft 22 may be constructed of a range of relatively rigidmaterials to provide firm support for the tibial mount 23. In someembodiments of the current invention, the main shaft 22 of the tibial IMrod is truncated to form a short extension for engaging an opening inthe upper surface of the tibia. As such, the tibial IM canal is notaccessed but rather the tibial mount 23 and the truncated tibial IM rodprimarily engage and interface with the external surface of the tibia.In other embodiments, the tibial mount 23 is provided without a tibialIM rod, such that a flat surface of the tibial mount 23 seats directlyon the resectioned surface of the tibia. As such, the interface betweenthe tibial mount 23 the tibia is completely extramedullary. In theseembodiments, the position of the tibial mount 23 with respect to thetibia is maintained by the perpendicular compression force between thetibial mount 23 and the tibia. In other embodiments, the flat surface ofthe tibial mount 23 is modified to include a plurality of spikes whichfurther interface with the resectioned tibial surface to preventundesirable movement of the tibial mount component 23 during tensioning.

Included in the tibial mount 23 are a thickened cylindrical portion 26and a plateau flange 28, as shown in FIG. 4. The cylindrical portion 26is preferably sized to fit the IM canal of the tibia 12. The cylindricalportion is connected at its distal end to the main shaft 22 and at itsproximal end supports the plateau flange 28. The plateau flange extendsoutward at right angles from the cylindrical portion 26 and has threeflat sides and one crescent-shaped side. The crescent shaped side is acutout to provide room for the anterior cruciate ligament prior toresection of the proximal tibia. The flat sides can further aid in guidepositioning and cutting, such as during a tibial compartmental resectionin a unicondylar arthroplasty procedure wherein only a single condyleand a portion of the tibial plateau are reconstructed.

A threaded opening 29 extends into the tibial mount 23 and provides acoupling attachment for the flexion bolt 30, which includes a threadedshaft 31, a hex flange 32 and a bushing 33, as shown in FIGS. 5 and 6.The threaded shaft 31 has a plurality of threads and extends away fromthe hex flange 32, while the bushing 33 is a smooth, cylindrical shaftthat extends opposite the threaded shaft from the other side of the hexflange 32. The hex flange 32 is shaped to allow gripping by a torque orother wrench to provide motivation for advancement of the threaded shaft32.

The threaded shaft 31 is configured to be advanced into the threadedopening 29 of the tibial mount 23 until it is flush with the plateauflange 28 thereby positioning the bushing 33 at its lowest profileposition, as shown in FIG. 5. This position allows the femur 11 andfemoral mount 15 extending therefrom to be slipped into position abovethe bushing 33. Then, the torque wrench is used to reverse theadvancement of the threaded shaft 31 until the bushing 33 engages thecylindrical portion 20 of the central opening 18 in the femoral mount15, as shown in FIG. 7. Advancement is reversed until a pre-selectedtorque measurement is reached on the torque wrench, or adequate tensionof the ligamentous structure is obtained. Once the appropriate ligamenttension is obtained, this torque value is recorded for comparison laterin the technique. The resulting assembly emulates a static linkage ofthe femur and tibia with the knee in flexion (e.g., at 30°, 60°, or 90°of flexion or increments therebetween) from which the surgeon canreference subsequent resection instruments as described below.

Also included in the assembly 10 is a quick connect locking mechanism 34that connects into the hex portion 19 of the central opening 18, asshown in FIGS. 8 and 9. Included in this embodiment of the lockingmechanism are a static outrigger arm 35, a spring-biased plunger 36 anda static clocking extension 37 which emulates the anti-rotation feature19, and in this instance has a hexagonal shape. The arm 35 has anelongate portion 38 and a rounded head portion 39. The elongate portion38 of the arm 35 has a square cross-section and extends from the roundedhead portion 39 which has a partially cylindrical shape with a pair ofopposing flats at its ends. Extending from one of the flats of therounded head portion is the hex extension 37. The hex extension 37 has ahexagonal cross-section configured to snugly fit within the hex portion19 of the central opening 18 defined in the femoral mount 15. As shownin FIG. 8, defined in one rounded surface of the head portion 39 is ahelically extending slot 43 which, as will be described below, guidesmotion of the plunger 36.

Defined through the rounded head portion 39 and the hex extension 37 isa cylindrical opening 40 through which the plunger 36 extends. Inparticular, the plunger 36 includes a thumb press 41, a shaft 42, aspring 45 and rotating extension 44 which emulates the anti-rotationfeature 37, in this instance is a hex, but could be any non-cylindricalshape, such as square, triangle or ellipse, capable of limitingrotation. The thumb press 41 is positioned at one end of the plunger 36and has the shape of a circular disk with ridges to promote pressingwith a thumb. Subjacent the thumb press 41 is the spring 45 which ispreferably in the shape of a coil and extends around the shaft 42 andbetween the thumb press and head portion 39 so as to bias them apart.

The shaft 42 includes a peg 46 that extends perpendicular to the shaftand into the helical slot 43 defined in the head portion 39, as shown inFIG. 8. Thus, depression of the thumb press 41 advances the shaft 42within the opening 40 in the head portion 39, and also results inrotation of the shaft as the peg 46 fixed thereto helically travels inthe helical slot 43. The hexagonal end 44 of the plunger 36 is fixed tothe end of the shaft 42 opposite the thumb press 41, extends along afree end of the hex extension 37 and has a hexagonal shape and sizematching that of the hex extension 37.

Due to its connection to the shaft 42, depression of the thumb press 41also causes rotation of the hexagonal end 44 of the plunger 36 until theflats of the hexagonal end match the orientation of the flats of the hexextension 37, as shown in FIG. 10. Matching of this orientation allowsinsertion of the hex extension 37 and the hexagonal end 44 into the hexportion 19 of the central opening 18 of the femoral mount 15, as shownin FIG. 11. Once the thumb press 41 is released, the spring 45 biasesthe thumb press, shaft 42 and hexagonal end 44 upwards, causing theflats of the hexagonal end to return to their non-matching, out-of-phaseposition (shown in FIG. 9) with respect to the flats of the hexagonalextension 37.

At this point, the hexagonal end 44 of the plunger 36 resides in thecylindrical portion 20 of the central opening 18 and, due to itsnon-matching position, cannot be withdrawn through the hex portion 19 ofthe central opening. As a result, the locking mechanism 34 becomesrotationally and translationally locked with respect to the femoralmount 15 and the femoral IM rod 13. Once locked in place, the arm 35 ofthe locking mechanism 34 extends anteriorly outward from the femoralmount 15 and the condyles of the femur 11. Notably, the combination ofthe relatively narrow femoral mount 15 and narrow, elongate structure ofthe arm 35 allows passage through relatively small surgical approachopenings, facilitating use of the assembly 10 with less invasiveprocedures. For example, a modified mid-vastus, medial mid-vastus orsubvastus approach could be used with a small 8-10 cm cut which allowsavoidance of a release of the quadriceps from the anterior tibia.

Also included in the assembly 10 of the illustrated embodiment of theinvention is a flexion guide support member 47 which is supported by thelocking mechanism 34. Included in the flexion guide support member is aslider member 48 and a ratchet bar 49. The slider member defines arectangular opening 50 which is sized and shaped to allow the slidermember to be supported by, and slide along, the rectangularcross-section of the arm 35 of the locking mechanism 34. This motionallows the ratchet bar 49, which is attached to the slider member 48, tomove toward and away from the knee joint. The slider member 48 ispreferably shaped to have finger grips (e.g., the tapered portion of theillustrated slider member) and may also include some type of a pin orlocking assembly to resist, but not prohibit its sliding relative to thearm 35. The ratchet bar 49 itself is also rectangular shaped incross-section and, when assembled, extends distally from the arm 35 ofthe locking mechanism 34, as shown in FIG. 12. The ratchet bar 49 alsoincludes a pair of chamfered corners supporting a plurality of adjacentratchet grooves 51 extending along the length of the ratchet bar.

The assembly 10 also includes a flexed knee cutting guide assembly 52that attaches to the flexion guide support member 47, as shown in FIGS.13, 14 and 15. The flexed knee cutting guide assembly 52 includes aquick release mechanism 53 and a cutting guide 54. The quick releasemechanism 53 includes a body 55, a draw pin 56, first and second springs57, 58, a locking lever 59 and a locking pin 60. As shown in FIG. 16,the body 55 defines a rectangular opening 61 which allows the body to beslid over the rectangular cross-section of the ratchet bar 49. Inaddition, the body 55 includes a side opening into which the draw pin 56extends so that its end engages the ratchet grooves 51. In particular,the first spring 57 biases the draw pin into a position normallyengaging the ratchet grooves so as to lock the draw pin, and hence thebody 55, into a particular position on the slider member 48. The lockingpin 60 extends through the body and through the draw pin 56 to securethe draw pin 56 and prevent it from disassembly.

The body 55 additionally includes a clevis 62 that extends outwards fromthe opposite side of the body from the draw pin 56 and which supportsrotation of the locking lever 59 about its middle portion. As well shownin FIG. 17, the locking lever has a curved finger grip biased outwardfrom the body 55 by the second spring 58 and the opposite end of thelocking lever includes a tapered tongue 63 which, as will be describedbelow, engages the cutting guide 54 so as to lock the quick releasemechanism 53 thereto. Extending away from the clevis 62, opposite thelocking lever, is an engagement member 64 of the body 55. The engagementmember 64 has a rectangular cross-section and, in the assembledcondition shown in FIG. 13, extends into a connection with the cuttingguide 54.

As shown in FIG. 13, the cutting guide 54 extends posteriorly (whenassembled) from the quick release mechanism 53 and includes a mountingportion 65, a k-wire guide or fixation pin portion 66, a crosspinportion 71, a proximal tibial cut guide portion 67 and a posteriorcondylar femoral cut guide portion 68. The mounting portion 65 defines arectangular opening 69 that is sized and shaped to slidably receive theengagement member 64 of the body 55 of the quick release mechanism 53.The mounting portion 65 also defines a notch 70 in one of the sidewallsof the rectangular opening 69, as shown in FIG. 18. The notch 70 issized, shaped and positioned to receive the tapered tongue 63 of thelocking lever 59 when the locking lever is under the bias of the secondspring 58, as shown in FIG. 15. Release of the cutting guide 54 iseasily accomplished by depressing the free end of the locking lever 59,overcoming the bias of the second spring 58 and disengaging the taperedtongue from the notch 70 of the mounting portion 65.

The fixation pin (or k-wire) guide portion 66, the tibial cut guideportion 67 and the femoral cut guide portion 68 each have a crescentshape that extends in a medial-lateral direction around the anatomicalcurvature of the anterior-medial or anterior-lateral tibia (dependingupon which cut is being made), as shown in FIG. 13. The fixation pinguide portion 66 is adjacent the mounting portion 65 and defines aplurality of fixation pin holes 72 that extend in a posterior directionat an angle so as to guide fixation pins (used to fix the cutting guide54 before release of the other components of the assembly 10) into thethickest anterior portions of cortical bone on the tibia 12. Althoughless preferred, the number and orientation of the fixation pin holescould be varied depending upon the firmness of the connection desired,size and morphology of the tibia 12, etc.

The tibial cut guide portion 67 is positioned adjacent the fixation pinguide portion 66 and defines a slot for guiding the tibial cut. The slotextends along the length of the crescent shape of the guide portion 67and generally has a parallel orientation with respect to the tibialplateau. However, the resection plane defined by guide portion 67 mayvary in posterior slope (sagittal plane angularity) and varus/valgus(coronal plane angularity), depending on the desired position andpreference of the surgeon for the cutting guide 54. An example of such acut is illustrated in FIG. 19, wherein the tibia has a flat planar cutextending in the anterior-posterior and medial-lateral planes on theproximal end of the tibia 12. The femoral cut guide portion 68 isproximally spaced from the tibial cut guide portion 67 by a pair ofconnection flanges 73 so as to bridge the knee joint compartment.Similar to the tibial cut guide portion 67, the femoral cut guideportion 68 defines a slot that extends along the length of the crescentshape. However, because the knee is in flexion, the cut is guidedthrough the posterior of the condyles of the femur 11.

An advantage of the components of the assembly 10 for positioning cutswith the knee in flexion, including the femoral mount 15, the tibialmount 23, the flexion bolt 30, the locking mechanism 34, the flexionguide support member 47 and the flexed knee cutting guide assembly 52,is their usability with relatively non-invasive, narrow cuts in theanterior soft tissues of the knee (and with a retracted patella).Generally, as can be seen in FIGS. 14 and 15, the assembled componentsfor making the cuts in knee flexion are relatively narrow as they extendout of the joint space in a U-shape, while at the same time providing afirm connection for supporting the cutting guide 54, a quick assemblyand release of the components and accurate positioning of the flexedknee cutting guide. Considering the cutting guide 54 by itself (whichcan be positioned inside of the capsular incision), the width of thiscomponent is small compared to conventional cutting guides, for example,within a range of up to 4 to 5 cm thereby allowing their use withminimally invasive approaches to the knee joint.

The assembly 10 also includes instrumentation configured to guide cutswith the knee in extension (i.e., with the tibia and femur generallyaligned, or at 0° of flexion), as shown in FIGS. 19-29. For kneeextension, both the femoral IM rod 13 and the tibial IM rod 14 remain inplace, as shown in FIG. 19. However, instead of attachment of the tibialmount 23 to the tibial IM rod 14, a tibial angulation guide 74 isattached to the tibial IM rod. The tibial angulation guide 74 includes agauge block 76 and a post 97 which fits into an extension bolt 96(similar to the flexion bolt 30, but without the bushing 33). Theextension bolt 96 also has a hex flange 75. Alternatively, a separategauge block 76 may be employed with a shaft (as shown in FIG. 6) thatextends into an opening in the bushing 33, allowing removal of the bolt30 to be avoided.

Regardless, gauge block 76 extends upward from the plateau flange 28 ofthe tibial mount 23 when the threaded shaft of the extension bolt 96extends into the threaded opening 29 and defines an arc surface 77 and aplurality of gauge marks 78 defined on its anterior surface, as shown inFIGS. 19-21. The arc surface 77 is shaped and sized to receive the outersurface of the cylindrically shaped femoral mount 15 and allow thefemoral mount 15 to rotate in the varus-valgus direction and slide inthe anterior-posterior direction therein. These motions are left free soas to not over-constrain the femur 11 and tibia 12, but still promoteanterior-posterior alignment of the instruments and rotational positionselection, for better positioning of the tibial and femoral cuts. Othervariations and combinations of shapes of the femoral mount 15 and tibialangulation guide 74 could be employed to allow these ranges of motion,such as by reversing the shapes of the gauge block 76 (it having acylindrical shape) and the femoral mount 15 (it having the arc shape),by having a rounded shape between two plates, extending the angulationreadings away from the instrument assembly, etc., and still be withinthe purview of the present invention.

Adjustment of the relative proximal-distal positioning of the femur 11and the tibia 12 is accomplished, similar to the technique in theflexion position, by adjusting the rotation of the hex flange 75 of theextension bolt 96 with a torque wrench. This motion advances or retractsthe threaded shaft of the tibial extension bolt 96 into and out of thethreaded opening 29 in the tibial mount 23 and advances the tibialangulation guide 74 toward the femoral mount 15. Preferably, the femur11 and tibia 12 are distracted until the torque wrench has a readingsimilar to that for the knee in flexion to ensure that the joint is notoverly tight in knee extension. With respect to the torque wrench andthe amount of joint space, the torque wrench may be equipped with anextender that extends the length of the wrench, has hex-shaped jaws atits end and is relatively thin or low profile. If this is the case, thetorque measurements may be adjusted to compensate for the additionallength of the extender. In either case, the objective is to match thetorque value obtained when the instrument construct constrained the kneein some degree of flexion, in this instance 90° of flexion or incrementstherebetween, and torque the bolt to a similar torque measurement thatwas reached on the torque wrench in the previous step, or until adequatetension of the ligamentous structure is obtained.

Referring again to FIGS. 20 and 21, the gauge marks 78 of the gaugeblock 76 radiate outward from the center of rotation of the femoralmount 15, starting at the outer surface of the femoral mount, and arepositioned on the anterior surface of the gauge block. The gauge marks78 of the gauge block 76 are configured to match up with gauge marks 21of the femoral mount 15 (as shown by the arrow) to indicate a valgusangle of the tibia 12 with respect to the femur 11. Generally, thevalgus angle should be within a range of 3 to 7 degrees, or even 2 to 9degrees, depending upon the knee's morphology, surgeon preference, etc.

Once the angulation and proximal-distal positioning of the tibia 12 withrespect to the femur 11 has been adjusted, an extension guide supportmember 79 is attached to the femoral mount 15 using a second lockingmechanism 84, as shown in FIGS. 22 and 23. Generally, the second lockingmechanism 84 includes the plunger 36 (and its components includinghexagonal end 44), hex extension 37 and helical slot 43 which aresimilarly numbered as they share a similar function with the samecomponents of the first locking mechanism 34. The second lockingmechanism 84 differs in that the head portion 39 is somewhat longer, iscylindrical and lacks the elongate portion 38 of the arm 35. Also, thesecond locking mechanism 84 includes a grip flange 86 positionedadjacent the plunger 36 to facilitate a finger grip when depressing theplunger. Regardless, the hexagonal end 44 has the same rotating motionthat facilitates quick attachment of the end of the second lockingmechanism 84 to the femoral mount 15.

The extension guide support member 79 includes a mounting portion 80, asupport arm 81 and a fixation flange 82. The mounting portion 80 has acylindrical shape with a cylindrical opening 83 extending therethroughthat is configured to slidably receive the second locking mechanism 84,but is not rotationally constrained by said second locking mechanism 84.Extending away from one side of the mounting portion 80 is the supportarm 81 which is an elongate structure with a T-shaped cross section.Extending away from the other side of the mounting portion 80 is anadditional flange 82 that acts as a housing for a mechanism, in thiscase a ball and spring 85, to provide some resistance to rotation of theextension guide support member 79 with respect to the second lockingmechanism 84.

Also included in the illustrated embodiment of the assembly 10, is anextended knee cutting guide 87 that is supported by the extension guidesupport member 79 during positioning, as shown in FIGS. 24-29. Theextended knee cutting guide 87 includes a mounting portion 88, afixation pin (or k-wire) guide portion 89, a femoral cut guide portion90 and a reference lever 91. The mounting portion 88 is generallycentered in a body portion of the extended knee cutting guide 87 anddefines a channel 92 that has a cross-sectional shape matched to theT-shaped cross-section of the support arm 81. The matching shapes allowthe extended knee cutting guide 87 to slide in the proximal-distaldirection along the support arm 81.

The fixation pin guide portion 89 defines a plurality of k-wire (orother type of fastener, e.g., screws, nails, etc.) holes 93 that allowfixation using fixation pins after positioning of the extended kneecutting guide 87. The holes 93 are positioned on medial and lateralsides of the anterior femur when positioned so as to allow fixation torelatively thick cortical bone, as shown in FIG. 25. As with the k-wireholes 72, the k-wire holes 93 can be oriented at various angles orselectively positioned to guide fasteners into and through largerlengths of denser bone on the femur 11.

The femoral cut guide portion 90 extends either laterally or mediallyfor a unicompartmental reconstruction (as with the illustratedembodiment), or in both directions for a full resection of the femoralcondyles. Notably, the guide portion 90 extends distally in the shape ofa U that fits around the second locking mechanism 84 when the extendedknee cutting guide 87 is in place, as well shown in FIG. 29. Regardless,the guide portion 90 extends distally from the k-wire guide portion 89and then laterally or medially to define a guide slot 94. The guide slot94 is of sufficient width to allow passage of cutting instruments orblades but still promote a relatively straight or planar resection.Notably, extension medially allows the laterally shifted patella to beavoided in a medially oriented approach to the knee joint compartment.

Extending further distally from the femoral cut guide portion 90 is aportion of the extended knee cutting guide 87 that defines a clevis 95that rotationally supports the reference lever 91. The reference leverextends laterally or medially and rotates in an anterior-posteriordirection to allow positioning in the joint compartment, as shown inFIGS. 24 and 25. The reference lever 91 has a broad, flat distal surfacethat is configured to rest against the flat tibial cut and a flatlateral surface is configured to abut the side surface of the plateauflange 28. These surfaces provide a stop for the distal movement of theextended knee cutting guide 87 along the support arm 81 of the extensionguide support member 79. With the reference lever 91 and the secondlocking mechanism 84 in place, fixation pins can be inserted through thepin holes 93 in the guide portion 89 to fix the femoral cut guideportion 90 to the femur 11. This allows removal of the extension guidesupport member 79, as shown in FIGS. 27, 28 and 29.

Advantageously, the components for positioning the cuts with the knee inextension, including the extension bolt 96, tibial angulation guide 74,the extension guide support member 79 and the extended knee cuttingguide 87 are configured for passage through an anterior and medialapproach to the knee compartment due to the narrow width and profile ofthe components. For example, as shown in FIG. 25, the posterior portionof the second locking mechanism 84 and the reference lever 91 would passthrough the incision and exhibit the aforementioned narrowness andlow-profile. Preferably, the width of this component is small comparedto conventional cutting guides, for example, within a range of up to 4to 5 cm thereby allowing their use with minimally invasive approaches tothe knee joint.

After these initial cuts, further cuts can then be made using theinitial cuts as a reference. As shown in FIGS. 30 and 31, an L-plate 99is employed to abut the posterior and distal flat surface of the femur11 to guide an anterior cut. Chamfer cuts (anterior and posterior) canbe made using a chamfer cut block and other finishing cuts can bereferences from the initial cuts made using the assembly 10 of thepresent invention. Additional description of these finishing cuts can befound in U.S. patent application Ser. No. 10/794,188 filed on Mar. 5,2004, entitled “Reference Mark Adjustment Mechanism for a FemoralCaliper and Method of Using the Same,” which is hereby incorporatedherein by reference.

In another embodiment of the present invention, as shown by FIGS. 32through 40, the assembly 10 includes additional modular options topromote quick assembly. As shown in FIG. 32, the femoral IM rod 13includes a secondary femoral mount 100. The secondary femoral mount 100has a saddle or crescent shape that extends laterally and distally froma central attachment to the distal end of the main shaft 16 of thefemoral IM rod 13. Defined in the inner, convexly curved surface of thesaddle is an opening 101 that is configured to receive a femoral mountrod 102 that supports the femoral mount 15, as shown in FIG. 33.

Referring again to FIG. 32, the tibial IM rod 14 includes a modifiedversion of tibial mount 23 supported by the shaft 22. In particular, theplateau flange 28 of the tibial mount 23 has a widened rectangular shapethat extends laterally outward from the threaded opening 29. Defined atthe anterior side of the plateau flange 28 are a pair of guide mountopenings 103 that extend posteriorly into the plateau flange. As shownin FIG. 34, the flexion bolt 30 may also be further modularized byproviding a post 104 for mounting the bushing 33 and hex flange 32within a central opening defined in a hex-head bolt 105 that includesthe threaded shaft 31 extending from its head 105. FIGS. 35 and 36 showthe assembly of the femoral mount 15 and tibial mount 32, along withtightening adjustment by elevation of the hex head bolt 105.

As shown in FIG. 37, the assembly 10 also includes a flexed knee cuttingguide assembly 52 that includes a flexed knee cutting guide 54 and adirect mount 106. The direct mount includes a pair of posts 107 that arespaced apart and extend from a mounting block 108. The spacing and sizeof the posts 107 are configured to extend into the guide mount openings103 defined in the plateau flange 28. Mounting block 108 can be coupledto tibial mount 32, such as by hermetically sealed magnets 111. Theflexed knee cutting guide 54 is attached to and extends distally fromthe mounting block 108. The flexed knee cutting guide defines aselection of slots 109 for guiding tibial and femoral cuts.

The posterior femoral cut can be accomplished by turning the flexed kneecutting guide assembly 52 upside down or by using another block whichwould be a modification of the upside down cutting guide assembly 52where the cutting guide 54 and selection of slots 109 is moved towardthe posts 107 and therefore, closer to the posterior femoral condyles ofthe knee. The selection of slots 109 of cutting guide assembly 52 can beas shown with the slots attached centrally or could be open centrallyand attached along both sides of the cutting guide 54.

As shown in FIGS. 38 and 39, the tibial IM rod 14 may also include avalgus adapter member 110 or a modified version of femoral mount 15 thathas its own post that is configured to insert into the central openingof the hex head bolt 105. As shown in FIG. 40, the valgus adapter member110 has a convex shape that is configured to extend into the concaveshape of the secondary femoral mount 100. This mating allowsvarus-valgus angulation to position the cuts when the knee is inextension, similar to the first embodiment disclosed above. Extendedknee cutting guides can be mounted similar to the flexed knee cuttingguide via posts 107.

The assembly 10 of the present invention has many advantages. Itprovides a relatively narrow and low profile collection of lockingcomponents that securely attach cutting guides to tibial and/or femoralIM rods. This provides a robust guide to reference cuts being made tothe tibia and the femur with an approach to the joint that minimizesinvasiveness. Further, many of the components, such as the first andsecond locking mechanisms 34, 84 and the quick release mechanism 53,facilitate quick assembly, easy adjustment and quick disassembly forimproved efficiency. The use of the bolts 30 and 96 or 105 and thetibial angulation guide 74 or valgus adapter member 110 allow the tibiaand femur to be distracted under a matching amount of torque in flexionand extension to ensure a better fit for the tibial and femoral kneereplacement components throughout a range of flexion. Also, the tibialangulation guide allows the surgeon to adjust the amount of valgusangulation of the tibia as desired to match the anatomy of the patient.

As shown in FIG. 41, in another embodiment of the present invention amodified femoral mount rod 102 and femoral mount 15 with a hingemechanism attaching mount 15 to the femoral mount rod 102 could be usedwith a retractor rod placed thru the hole 18 in the femoral mount 15 andguided posterior to the tibia thus providing a fulcrum and lever arm forthe retractor to displace the tibia forward or anterior to allowexposure for placement of the tibial component of the total kneearthroplasty after the bone cuts have been made. Since the IM rods fixrigidly to the bone, other retractors could also be attached to theGuide Assembly to facilitate knee exposure during the knee surgery.

As shown in FIG. 42, in another embodiment of the present inventionmini-trial components or trial components which are smaller but shapedwith identical thickness and radii to the actual knee arthroplastyimplants, designed to fit in holes 101 of femoral IM rod 13 and 29 oftibial IM rod 14 and articulate in the center portion of the knee couldbe used to check alignment and ligament stability prior to placement ofthe actual final knee arthroplasty implants. This design of a centrallyplaced mini-knee arthroplasty implant system could become a stand alonetotal knee arthroplasty. One advantage of this embodiment of the presentinvention is that the smaller instruments take up less space. Themini-trial femoral component could be designed with cutting surfaces orslots for making the chamfer cuts and other finishing cuts, thuseliminating the need for a chamfer cut block and L-plate 99 shown inFIGS. 30 and 31.

Referring now to FIGS. 43-48, another embodiment of the presentinvention is shown. Specifically, FIGS. 43-45 illustrate animplementation of the current invention for resecting a patient's kneein flexion, and FIGS. 46-48 illustrate an implementation of the currentinvention for resecting a patient's knee in extension. The femoral mount150 of the femoral IM rod 113 of each embodiment comprises a planarflange that is substantially inset, and flush with the insertion site ofthe femur 11. In one embodiment, a rongeur is used to prepare the distalfemur for a ⅜ inch drill entry. Following insertion of the drill, aplanar is then used to clear the remaining bone from the insertion siteand to provide a recessed surface into which the femoral mount 150 isseated. A threaded opening 129 extends into the femoral mount 150 andprovides a coupling attachment for an extension bolt 130, which includesa threaded shaft 131, a circular flange 132 with mounting holes 133, anda centralizing ball 134, as shown in FIGS. 46 and 47. Additionally, thethreaded opening 129 provides a mounting channel into which anon-threaded post 114 of a threaded barrel 115 is inserted. Theinteraction between the non-threaded post 114 and the threaded opening129 sufficiently retains the threaded barrel 115 within the femoral IMrod 113 and permits axial rotation of the threaded barrel 115 relativeto the IM rod 113. Axial rotation is desirable to permit limitedmovement of the surgical tool relative to the natural physiology of thepatient's knee. As such, the threaded barrel 115 is permitted to rotateand facilitate the natural alignment of the patient's knee throughoutthe tensioning process, as described below.

The threaded barrel 115 comprises a non-threaded post 114perpendicularly coupled to an outer surface of a threaded opening 116.The threaded opening 116 extends through the threaded barrel 15 andprovides a coupling attachment for a flexion bolt 120. The flexion bolt120 includes a threaded shaft 121, a circular flange 122 with mountingholes 123, and a non-threaded tip 124. The threaded shaft 121 compatiblythreads through the threaded opening 116 such that the non-threaded tip124 exits and extends beyond the threaded barrel 115. The circularflange 122 is perpendicularly attached to the threaded shaft 121opposite the non-threaded tip 124. The flange 122 is circular andgenerally disk-shaped having a plurality of mounting holes 123 evenlyspaced around the circumferential edge of the flange 122. The mountingholes 123 are sized and configured to compatibly receive a torque wrench140 or other device for turning the flexion bolt 120.

The current embodiment further comprises a tibial tensioning adapter160. The tibial tensioning adapter 160 is stably supported by the tibialIM rod 170 and positioned generally perpendicular to the main shaft ofthe tibial IM rod 170. The tibial tensioning adapter 160 comprises abase member 161 and a resection block guide 165. The base member 161 isgenerally planar and disc-like, having a centrally located opening 162that extends into the main shaft of the tibial IM rod 170. A bushing 125is further provided to compatibly seat within the opening 162. Thebushing 125 comprises a post portion 126 having a first diameter, and asleeve portion 127 having a second diameter and an opening 128. Thediameter of the post portion 126 is selected to compatibly insert withinthe opening 162 of the base member 161, while the diameter of the sleeveportion 127 is selected to be greater than the diameter of the opening162. As such, the sleeve portion 127 rests on the upper surface of thebase member 161 and is prevented from inserting into the opening 162.The opening 128 of the sleeve portion 127 is non-threaded and sized tocompatibly receive the non-threaded tip portion 124 of the flexion bolt120. Additionally, the interaction between the post 126 and the opening162 does not utilize threads thereby allowing the bushing 125 to freelyrotate within the opening 162 of the tibial tensioning adapter 160, andallowing the non-threaded tip 124 of the flexion bolt 120 to freelyrotate within the opening 128 of the bushing 125. These freely rotatinginteractions prevent rigid structuring or position of the surgical toolsthereby further permitting the natural physiology of the patient's kneeto be maintained during the tensioning and resection processes. Thus,the flexion bolt 120, the threaded barrel 115, and the bushing 125 arecombined with the femoral mount 150 and the tibial tensioning adapter160 to apply tension to the patient's knee preparatory to performing thedesired resections.

The base 161 further comprises a pair of spacers 163 forming a portionof the base member upper surface. The spacers 163 are generally pyramidshape and linerally configured on opposing sides of the opening 162. Thespacers 163 are provided to create a gap between the circular flange 132of the extension bolt 130 and the upper surface of the base member 161,as shown in FIG. 47. The pyramidal shape of the spacers 163 permitslimited radial movement of the extension bolt 130 relative to the basemember 161. This limited movement is desirable to accommodate thenatural physiology of the patient's knee throughout the tensioningprocess, described below in connection with FIGS. 46 and 48.

The resection block guide 165 is fixedly coupled to an edge surface ofthe base member 161 and extends outwardly therefrom. The block guide 165is generally aligned with the spacers 163 and positioned to extendoutwardly from the anterior surface of the knee. The block guide 165further comprises a plurality of notches 166 occupying an upper surfaceof the guide 165. The notches 166 span a portion of the upper surfaceand provide a coupling attachment for a resection block 180, as shown inFIGS. 45 and 48. The notches 166 further provide a plurality ofreference points or positions by which to gauge the position of theresection block 180.

Referring now to FIG. 44, an embodiment of the assembled invention isshown. Once the surgical device is assembled, a torque wrench 140 isinserted into a hole 123 of the circular flange 122 and the flexion bolt120 is rotated. Alternatively, in one embodiment the flexion bolt 120 isinitially rotated by hand until the femur 11 begins to lift away fromthe tibia 12. The torque wrench 140 is then utilized to further rotatethe flexion bolt 120 to a desired tension. This will typically result ina final tension of about 10-20 in/lbs. The amount of tension will differfor each patient based on individual physiology, injury, and ligamentviscoelasticity of the knee. Once the final tension in flexion has beenattained, the final amount of tension placed on the ligaments in isrecorded for future reference.

Referring now to FIG. 44A, an embodiment of the assembled invention isshown. In this embodiment, the flexion bolt 120 is substituted with aratcheting device 142. The ratcheting device 142 generally comprises ahandle portion 143, a biasing portion 144, and a gear box 145. Thebiasing portion 144 of the ratcheting device 142 is interposed betweenthe threaded barrel 115 and the bushing 125. The handle portion 143 isthen actuated to cause the biasing portion 144 to lift the femur 11 awayfrom the tibia 12. The gear box 145 converts the motion, or actuation ofthe handle portion 143 to change the position of the biasing portion 144and separate the knee joint.

The handle portion 143 may include any configuration whereby a physicianmay manipulate the handle portion 143 to actuate the biasing portion 144of the device 142. For example, in one embodiment the handle portion 143comprises a pair of opposing levers 146 and 147, each having a grip 148at a distal end and extending into the gear box 145 at a proximal end.The biasing portion 144 of the device 142 is actuated by gripping thehandle portion 143 and squeezing, such that the pair of opposing levers146 and 147 is brought to a proximal position. The action of theopposing levers 146 and 147 manipulates the gear box 145 causing thebiasing portion 144 to move away from a proximal position. Additionally,in one embodiment the gear box 145 includes a release for returning thebiasing portion 144 to a proximal position.

In another embodiment, the handle portion 143 comprises a single shafthaving a handle at the distal end, and extending into the gear box 145at the proximal end. In this embodiment, the biasing portion 144 of thedevice 142 is actuated by rotating the handle portion 143 in a clockwiseor counter-clockwise direction. The rotating action of the handleportion 143 manipulates the gear box 145 causing the biasing portion 144to move away from, or towards a proximal position. In one embodiment,the gear box 145 further includes a pawl or other device for maintainingthe biased position of the biasing portion 144 during use. As such, aphysician may actuate the device 142 to separate the knee to a desiredposition or tension, and then maintain the tension hands-free.

The biasing portion 143 may include any configuration capable ofmounting into the threaded barrel 115 and the bushing 125. For example,in one embodiment the biasing portion 143 includes a pair of jaws 148having a first end for engaging the threaded barrel 115 and the bushing125, and having a second end extending into the gear box 145. In anotherembodiment, the first end further includes a jointed connector 149 forengaging the threaded barrel 115 and the bushing 125. The jointedconnector 149 permits the pair of jaws 148 to separate the knee joint,yet provide limited movement of the knee joint to accommodate thenatural physiology of the patient's knee throughout the tensioningprocess.

The gear box 145 may include any configuration of gears compatible withthe handle portion 143 and the biasing portion 144 to achieve controlledseparation of the knee joint. The gear box 145 may also include anymeans for limiting or measuring the tension placed on the knee joint.For example, in one embodiment the gear box 145 further comprises atension meter 151 whereby the tension placed on the knee joint, by theratcheting device, 142 is displayed. In another embodiment, the gear box145 further comprises an adjusting screw 152 whereby the maximum allowedtension of the ratcheting device 142 is set. In this embodiment, aphysician adjusts the adjusting screw 152 to a desired tension. Onceset, the physician actuates the ratcheting device 142 to separate theknee joint. When the desired tension is achieved, further tensioning byactuation of the ratcheting device 142 is prevented, thus maintainingthe desired tension for the knee.

Referring now to FIG. 45, the resection block 180 is attached to theresection block guide 165 and slid into position against the anteriorsurface of the femur 11. The resection block 180 is secured to theresection block guide 165 by tightening a set screw 183 against thenotches 166 of the guide 165. The resection block 180 is then secured tothe femur 11 via a plurality of screws 181. Once the resection block 180is secured in position, the flexion bolt 120 is removed from thesurgical tool assembly and the cutting guides 182 of the resection block180 are used to resect the exposed distal surfaces of the lateral andmedial condyles.

Referring now to FIGS. 46-48, an implementation of the current inventionis provided for operation in knee extension. Referring to FIG. 46, theextension bolt 130 is shown prior to being interposed between thefemoral mount 150 and the tibial tensioning adapter 160. The extensionbolt 130 generally comprises a threaded shaft 131, a circular flange 132and a centralizing ball 134. The threaded shaft 131 is configured tocompatibly thread within the threaded opening 129 of the femoral mount150. The circular flange 132 is perpendicularly attached to the threadedshaft 131 and interposed between the threaded shaft 131 and thecentralizing ball 134. The flange 132 is disk shaped having a pluralityof mounting holes 133 evenly space around the circumferential edge ofthe flange 132. The mounting holes 133 are sized and configured tocompatibly receive a torque wrench 140 or other device for turning theextension bolt 130.

The centralizing ball 134 comprises a hemispherically shaped surfacethat is sized and configured to partially insert within opening 162 ofthe tibial tensioning adapter 160. As such, the centralizing ball 134partially engages the opening 162 yet remains sufficiently free toprovide axial rotation between the femur 11 and the tibia 12. Theinterface between the centralizing ball 134 and the opening 162 furtherensures accurate alignment of the femoral mount 150 with the tibialtensioning adapter 160. Radial rotation is further provided to the femur11 and the tibia 12 due to the interface 158 between the circular flange132 and the spacers 163, as previously discussed and as shown in FIG.47. Thus, the extension bolt 130 provides both alignment and limitedfree adjustment to the femur 11 and tibia 12 during the tensioning andresection procedures.

In one embodiment, the extension bolt 130 is first coupled to thefemoral mount 150 by threading the threaded shaft 131 into the threadedopening 129 of the femoral mount 150, with the knee in flexion, as shownin FIG. 46. The extension bolt 130 is maximally inserted into thethreaded opening 129 to minimize the distance between the femur 11 andthe tibia 12. The knee is then brought into extension and thecentralizing ball 134 is inserted into opening 162, as shown in FIG. 47.A torque wrench 140 is then utilized to rotate the extension bolt 130and apply tension the knee. The torque wrench 140 is inserted into ahole 133 of the circular flange 132 and turned to gradually remove theextension bolt 130 from the threaded opening 129. In one embodiment, thephysician immobilizes the resection block guide 165 to prevent rotationof the tibia 12 during rotation of the extension bolt 130. The physiciancontinues to turn the extension bolt 130 until the desired tension isplaced on the ligaments of the knee. Alternatively, a ratcheting device(see FIG. 44A) may be used with the knee in extension to place thedesired tension on the ligaments of the knee. In one embodiment, thefinal tension in extension is equal to the final tension in flexion. Inanother embodiment, the final tension in extension is different than thefinal tension in flexion.

Referring now to FIG. 48, the resection block 180 is attached to theresection block guide 165 and slid into position against the anteriorsurface of the femur 11, as discussed above in connection with FIG. 45.Once positioned, the resection block 180 is secured to the femur 11 withscrews 181 and the anterior surfaces of the lateral and medial condylesare resectioned.

In another embodiment, since the guide assembly is fixed rigidly to thebone and left in place during the essential steps of the kneepreparation, computer assisted guides are attached to the guide assemblyinstruments thus facilitating computer assisted total knee replacement.In other embodiments of the present invention, the guide assemblyinstruments are modified for use in a partial or unicompartmental kneearthroplasty procedure.

In some embodiments, the Guide Assembly Instruments can be modified foruse with short IM rods or a tibial platform instead of an IM rod forextramedullary knee preparation.

In some embodiments, the Guide Assembly holds a patient's leg in place.This decreases the need for medical assistants to hold the patient'sleg.

Following a completed resection of the patient's knee joint, theresectioned portions of the femur 11 and the tibia 12 are replaced by aknee prosthesis or implant 200, such as shown in FIGS. 49 and 50. Theknee implant 200 generally comprises a femoral component 202 and atibial component 204. Although the instruments of the invention can beused with any type of knee prosthesis 200, the instruments areparticularly well-suited for use in accurately resecting the knee forreceipt of a knee prosthesis that employs a constant radius throughoutthe primary range of flexion, such as Wright Medical Technology, Inc.'sADVANCE® medial pivot knee implant. The features and characteristics ofconstant radius knee prostheses are well known to those of skill in theart, but have not previously been used with knee tensioning resectioninstruments. As will be described below, a synergistic and previouslyunappreciated effect is obtained by using the tensioning instruments incombination with prior art constant radius knee implants. It isanticipated that the end result of this synergistic combination will begreater overall accuracy in the implantation of constant radius kneeimplants, with resulting improvements in clinical outcomes.

One of the benefits of a properly designed and implanted constant radiusknee prosthesis is that it provides the patient with constant ligamenttension throughout the primary range of flexion. As discussed herein,the use of the instruments of the invention to resect the knee whileunder optimum tension helps insure accurate placement of the kneeimplant components. The combined use of tensioning instruments andconstant radius knee implants improves the likelihood of achievingconstant ligament tension throughout the primary range of flexion.Various embodiments of knee implants that incorporate a constant radiusare discussed in the following prior art documents, which areincorporated herein by reference: U.S. Pat. Nos. 7,261,740; 6,013,103;6,013,103; 5,824,100; 5,330,533; 5,326,361; 5,314,482; 5,219,362;5,133,758; 4,085,466; German Patent Application 3314038A1.

In the prior art ADVANCE® Medial Pivot knee implant, the femoralcomponent 202 has a spherical condyle 206 on the medial side. Asindicated in FIG. 51, in the sagittal or A-P plane, the medial femoralcondyle 206 has a constant radius 226 over at least the primary range offlexion, which extends from about 0 degrees in extension to about 90degrees in flexion, depending on the patient. The lateral femoralcondyle 222 also has an A-P constant radius 226 throughout the primaryrange of flexion. The medial side of the tibial base 204 of the ADVANCE®Medial Pivot knee has a shallow spherically concave bearing surface 232,which is sized to closely receive the medial femoral condyle 206 in aball-and-socket manner. The lateral side of the tibial base 204 isgenerally in the form of an elongated arcuate trough 230. These featuresallow the medial femoral condyle 206 to pivot in the medial tibialbearing 232 during flexion, while simultaneously permitting the lateralfemoral condyle 222 to translate posteriorly in the lateral tibialbearing 218. This action is designed to mimic the function of thenatural knee, in which the medial femoral condyle exhibits less rollbackthan the lateral condyle during motion. Features and characteristics ofthe ADVANCE® Medial Pivot knee are discussed in greater detail in U.S.Pat. Nos. 5,964,808 and 6,013,103, which are incorporated herein byreference. Although the ADVANCE® Medial Pivot knee implant is anexemplary implant design for optimizing and complementing the use of thetensioning instruments of the invention, other constant radius kneeimplant designs can be used to similar or equal effect.

One of the drawbacks of prior art knee instruments is that overstuffingor under filling the joint sometimes occurs, with resulting tightness orlaxity, respectively, in the ligaments. As discussed above, use of thetensioning instruments to resect with the knee tensed in the extendedposition allows the user to make a balanced extension gap resection whencompared with the tensed resections made with the knee previouslypositioned in flexion. The resection cuts are made off of a singlereference point, the single reference point being the desired amount oftension. The use of equal flexion and extension gaps automaticallybalances the mid-flexion gap at all points in between. By thenimplanting a constant radius knee implant onto the resectioned knee, thesurgeon effectively transfers the optimum tension obtained by thetensioning instruments to the constant radius knee implant, resulting ina stable, smoothly functioning knee throughout at least the primaryrange of flexion. In mechanical terms, the tensioning technique preloadsthe bearing, the bearing being the constant radius knee implant.

In contrast, if a conventional J-curve or varying radius knee implant isused with the tensioning technique, rather than a constant radiusimplant, it becomes necessary to vary the cuts instead of using an equalflexion and extension gap. The use of a varying radius knee implant thusnecessarily complicates the process and the use of the instruments.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

What is claimed is:
 1. A device for maintaining a ligamentous tension ofa knee joint, the device comprising: a femoral component defining anopening, wherein a portion of the femoral component that defines theopening is configured to extend into a femur when at least part of thefemoral component is seated in the femur; a tibial component configuredto be seated on a portion of a tibia; and a tensioning apparatusconfigured to couple to the femoral component and the tibial componentand that is configured to be selectively actuated to vary a distancebetween the femoral component and the tibial component to apply aligamentous tension to the knee joint.
 2. The device of claim 1, whereinthe tensioning apparatus comprises a threaded element that is configuredto twist in a first direction to increase a distance between the femoralcomponent and the tibial component.
 3. The device of claim 1, whereinthe tibial component comprises a planar surface that is configured tocontact a proximal, resected end of the tibia when the tibial componentis seated on the portion of the tibia.
 4. The device of claim 1, whereinthe opening receives an elongated shaft, and wherein the elongated shaftis coupled to the tensioning apparatus.